SR 6/7: Albo 2013- sperm storage and cryptic female choice for nuptial gifts Flashcards
where nuptial gifts facilitate female mating what may females gain?
indirect benefits through prefered storage of sperm from gift giving males if they are a signal of quality
what was the study species?
spider P.mirabilis
what did the study quantify?
number of sperm stored in response to copulation with males with and without gift
what did they assess the effect of gift presence and copulation duration on?
egg hatching success in uninterrupted matings with gift giving males
what % higher egg hatching success was there for females who mated with gift giving males?
17%
what did uninterrupted copulations result in?
increased sperm storage and egg hatching success
how and under what conditions can the nuptial gifts be considered a male signal?
under +ve SS
by cryptic sperm storage
what does giving gifts benefit to the males?
- longer copulations
- increased sperm transfer
- higher mating success
- more eggs fertilised
what is cryptic mate choice?
SS during mating or post mating
what can nutritious gifts be a signal for?
male quality in terms of good hunting ability
what may gift giving be a target for and evolution of what will it favour?
sexually antagonistic coevolution
evolution of fake gifts
what can internal processes resulting in fertilisation bias be mediated by?
both sexes
why are there few studies on female cryptic sperm choice?
hard to disentangle male and female driven processes
what is the gift that this spider species offers?
insect wrapped in silk that female feeds on during copulation
how do males transfer sperm?
externally using pedipalps loaded with sperm
where do females store sperm?
spermatheca storage organ
how do males court?
offer gift in chelicerae whilst waving pedipalps
what does the male do once the female has accepted the gift?
initiates sperm transfer inserting pedipalps into female genital tract
what test was used for normal distribution of residuals
Shapiro wilk
what test was used for homogeneity of variances?
Levene’s test
what were generalised linear models used for?
to analyse sperm number, hatching success and effect of copulation duration on hatching success
what was linear regression used for?
effect of copulation duration on number of sperm stored
how did they calculate sperm count?
dissected female sperm storage organs and counted sperm under microscope
what was found for sperm count? (2)
- if doesnt give give less sperm count and less stored in female genital tract
- most sperm stored when females mated with gift giving males uninterrupted
how was hatching success calculated?
total eggs in first egg sac produced counted and success is the proportion of hatched eggs
what is the relationship between copulation duration and hatching success?
positive
where was hatching success highest?
gift giving groups with uninterrupted copulation
what are the indirect benefits the female may gain? (2)
- by fisherian processes if produce sexy sons more likely to provide gifts
- elevated offspring fitness if gift giving males pass on genes
why was it suggested females select males based on their quality?
satiated males had higher mating and paternity success compared to starved males
what does the data suggest sperm storage is at least partially under the control of?
female through cryptic sperm choice
what may differential sperm storage be due to?
- preferential sperm uptake during mating
- post copulatory differential sperm selection
how can males increase their fertilisation success through increasing sperm transfer? (4)
- longer copulation
- higher rate of ejaculate transfer
- increased sperm size
- different types of sperm produced in 1 ejaculate
what do males tailor the number of sperm in pedipalps to?
in response to being able to acquire a gift
what is copulation duration positively correlated with?
nuptial feeding and gift quality
which males can gain an advantage in sperm competition?
males that can offer nuptial gifts that take longer to consume
how do both males and females benefit from sperm storage and longer copulations?
increased sperm transfer so higher paternity and indirect benefits to the female
what acts to maintain selection for high quality gifts?
combination of cryptic female sperm storage favouring gift giving males and advantaged in sperm competition to those offering genuine gifts
what was determined in the female sperm storage organs
the number of sperm
what were each of these groups of males:
a) NG males
b) GT males
c) G males
a) no gift and copulate without interruption
b) gift and copulation terminated after 10 mins
c) gift and uninterrupted copulation
what differed among the 3 experimental groups?
number of sperm
which group stored significantly higher sperm and had higher hatching success?
G males
with uninterrupted matings with gift giving males
what are males copulating without gifts likely under selection pressure to do?
increase sperm transfer rate
who controls copulation duration?
females
what is expected if worthless gifts are given?
cryptic female choice
